U.S. patent application number 10/906237 was filed with the patent office on 2005-11-03 for filter material absorb hydrocarbon.
Invention is credited to Chan, Chiu Y., Lebowitz, Jeffrey L., Lovette, Joseph W..
Application Number | 20050241480 10/906237 |
Document ID | / |
Family ID | 35185747 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241480 |
Kind Code |
A1 |
Lebowitz, Jeffrey L. ; et
al. |
November 3, 2005 |
FILTER MATERIAL ABSORB HYDROCARBON
Abstract
A porous filter medium in a canister forms a filter for
extracting hydrocarbons from vapors emitted from a motorized
vehicle, device or appliance fuel tank. The filter medium is a
polymer network of a foam, nonwoven or collection of particles, and
the filter has a butane working capacity (W/W %) of 4.0 percent or
higher.
Inventors: |
Lebowitz, Jeffrey L.;
(Drexel Hill, PA) ; Lovette, Joseph W.;
(Earleville, MD) ; Chan, Chiu Y.; (Wilmington,
DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
P O BOX 2207
WILMINGTON
DE
19899
US
|
Family ID: |
35185747 |
Appl. No.: |
10/906237 |
Filed: |
February 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10906237 |
Feb 10, 2005 |
|
|
|
10833857 |
Apr 28, 2004 |
|
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Current U.S.
Class: |
95/146 |
Current CPC
Class: |
B01D 2253/202 20130101;
B01D 2257/702 20130101; B01D 53/02 20130101 |
Class at
Publication: |
095/146 |
International
Class: |
B01D 053/02 |
Claims
What is claimed as new and desired to be protected by letters
patent of the united states is:
1. A method for removing hydrocarbons from a gaseous stream emitted
from a fuel tank during refueling a motor vehicle, device or
appliance with a hydrocarbon-based fuel consuming engine,
comprising: installing a filter in a flow path established between
the fuel tank and an exhaust from the fuel tank, wherein said
filter comprises a polymer network within a canister and said
filter has a butane working capacity (W/W %) of at least 4.0
percent.
2. The method of claim 1, wherein the polymer network comprises a
foam with a pore size between about 3 and about 300 ppi.
3. The method of claim 1, wherein the polymer network comprises a
foam with a pore size between about 20 and about 90 ppi.
4. The method of claim 1, wherein the polymer network has an air
permeability of 0.1 to 20 inches water pressure drop.
5. The method of claim 1, wherein the polymer network has an air
permeability of 0.1 to 5 inches water pressure drop.
6. The method of claim 1, wherein the polymer network is formed
from a material selected from the group consisting of urethanes,
melamines, polyvinylchloride, acrylics, polyolefins, polyimides,
ethylene vinyl acetate, polyvinyl acetate, polyvinyl alcohol and
combinations of polymers and polymer derivatives.
7. The method of claim 2, wherein the foam is selected from the
group consisting of polyether polyurethane foam, polyester
polyurethane foam and melamine foam.
8. The method of claim 7, wherein the foam is reticulated.
9. The method of claim 1, wherein the polymer network comprises a
nonwoven polymer, a collection of polymer particles, a collection
of shredded particles of foam, a monolith of foam, multiple layers
of foam, a coiled sheet of foam, or any combination thereof.
10. The method of claim 1, wherein a coating is applied to at least
a portion of the polymer network.
11. The method of claim 10, wherein the coating comprises one or
more materials selected from the group consisting of activated
carbons, silicas, silicates, aluminosilicates, filter agents,
molecular sieves, flame retardants, electrically conductive
materials, antimicrobial additives, germicides, pigments and
colorants.
12. A method for removing hydrocarbons from a gaseous stream
emitted from a fuel tank during refueling a motor vehicle, device
or appliance with a hydrocarbon-based fuel consuming engine,
consisting essentially of: installing a filter in a flow path
established between the fuel tank and an exhaust from the fuel
tank, wherein said filter comprises a cellular polymer foam in a
canister, and wherein the foam has a pore size from 20 to 90 ppi
and the filter has a butane working capacity (W/W %) of at least
8.0 percent.
13. A system for extracting evaporative hydrocarbon emissions from
a motorized vehicle, device or appliance, comprising: a filter
comprising a polymer network within an inner chamber of a housing;
an inlet through which a gas stream containing a hydrocarbon enters
the inner chamber; an outlet from which a gas stream exits the
inner chamber; and wherein said filter has a butane working
capacity (W/W %) of at least 4.0 percent.
14. The system of claim 13, wherein the polymer network comprises a
foam with a pore size between about 3 and about 300 ppi.
15. The system of claim 13, wherein the polymer network has an air
permeability of 0.1 to 20 inches water pressure drop.
16. The system of claim 13, wherein the polymer network is formed
from a material selected from the group consisting of urethanes,
melamines, polyvinylchoride, acrylics, polyimides, polyolefins,
polyvinyl acetate, polyvinyl alcohol, ethylene vinyl acetate, and
combinations of polymers and polymer derivatives.
17. The system of claim 14, wherein the foam is selected from the
group consisting of polyether polyurethane foam, polyester
polyurethane foam and melamine foam.
18. The system of claim 17, wherein the foam is reticulated.
19. The system of claim 13, wherein the polymer network comprises a
nonwoven polymer, a collection of polymer particles, a collection
of shredded particles of foam, a monolith of foam, multiple layers
of foam, a coiled sheet of foam, or any combination thereof.
20. The system of claim 13, wherein a coating is applied to at
least a portion of the polymer network.
21. The system of claim 20, wherein the coating comprises one or
more materials selected from the group consisting of activated
carbons, silicas, silicates, aluminosilicates, filter agents,
molecular sieves, flame retardants, electrically conductive
materials, antimicrobial additives, germicides, pigments and
colorants.
22. The system of claim 13, wherein the filter is formed as one or
more disks insertable into the housing inner chamber in stacked
relation.
23. The system of claim 13, wherein the housing inner chamber is
generally cylindrical and a rolled sheet of the polymer network is
inserted into said chamber.
24. The system of claim 13, wherein the filter is formed as a
monolithic part formed with outer dimensions so as to fit within
the housing inner chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/833,857, filed Apr. 28, 2004, now
pending.
FIELD OF THE INVENTION
[0002] This invention relates to a filter material to capture
hydrocarbon evaporative emissions, such as during refueling, to
prevent or limit such hydrocarbons from being emitted into the
atmosphere, and to an evaporative emission control system
incorporating such filter material.
BACKGROUND OF THE INVENTION
[0003] Environmental Protection Agency ("EPA") regulations require
gasoline and diesel powered passenger cars and light trucks to
incorporate on board hydrocarbon refueling emissions controls. As
fuel is introduced into a motor vehicle's tank, the displaced
vapors from the tank are directed to the refueling emissions
controls. The goal is for the on board system to capture about 95
percent of the refueling emissions to limit the amount of volatile
organic compounds ("VOCs") and toxins emitted into the atmosphere
during refueling. The VOCs that evaporate from gasoline during
vehicle refueling contribute to urban ozone or smog formation.
[0004] Currently, vehicles use activated carbon-filled canisters to
capture evaporative emissions. Carbon is "activated" by treating
with steam or chemicals to increase porosity and generate a high
surface area so that the activated carbon more readily adsorbs
various chemical species. The activated carbon in the canister
either is in the form of loose powders, granules or pellets, or in
the form of a honeycomb extrusion, or a combination of these. The
gas tank and fill pipe are designed so that when refueling the
vehicle, fuel vapors in the tank travel to the activated
carbon-packed canister where the vapors are adsorbed. Each filled
canister weighs up to about 10 pounds. The carbon granules or
pellets settle after being subjected to vehicle movement, which can
change the flow path and alter filter performance. Carbon powders,
granules or pellets generate dust, and the honeycomb extrusions
lack significant vibrational stability, leading to breakage and
dust generation. Lower cost, lighter weight, more resilient and
more reliable alternatives to the activated carbon-packed canisters
are sought.
[0005] One activated carbon canister system is shown in U.S. Pat.
No. 6,540,815 (Hiltzik). In this patent, an emissions control
system canister has a vent side that incorporates multiple beds of
adsorbent materials that may be spaced apart by inert fillers or
voidages, or has an adsorbent-containing monolith, such as a
honeycomb, that has a desired void volume. When used, the inert
fillers can be porous mats of foam. Such vent side absorbents are
stated to have butane adsorption of about 6 g/dL. The '815 patent
mentions activated carbon formed from various raw materials,
including porous polymers, as a hydrocarbon adsorbent. In the
working examples, the '815 patent uses foams only as inert or
nonadsorbing material in combination with adsorbing activated
carbon pellets. Such foams are not identified as hydrocarbon vapor
adsorbents.
[0006] U.S. Pat. No. 6,464,761 (Bugli) discusses an air induction
filter assembly that includes a reticulated multi-layer foam with
carbon impregnation to remove residual hydrocarbon vapors diffusing
through the inlet manifold of an engine after the engine is shut
off. The '761 patent states that the carbon impregnated foam layer
is optional in non-automotive applications where hydrocarbon
adsorption is not required.
[0007] Foams have been used as fluid filtering media for different
applications. SIF.RTM. foams from Foamex International Inc. of
Linwood, Pa. are reticulated flexible polyester or polyether
urethane foams with pore sizes from 10 to 110 pores per linear inch
that may be used, for example, as gasoline fuel filters in
chainsaws and other small engines. These foams filter particulates
from liquids. PROTECTAIR.RTM. II foams, also from Foamex
International, are reticulated polyether foams with pore sizes from
20 to 35 pores per linear inch that may be used, for example, in
air filters to filter particulates from an air stream. Heretofore,
such foams have not been used to absorb hydrocarbons entrained in a
gas stream.
[0008] In the 1980's, Scottfoam Corporation, a predecessor to
Foamex International, offered an activated charcoal impregnated
SIF.RTM. foam for use as a shoe sole insert under the trademark
SORBACELL.TM.. The Technical Data Sheet for this foam indicates
that the foam was impregnated with high loadings (2 oz./square
yard) of finely divided activated carbon particles, which allowed
the coated foam to remove particulate material and adsorb some
gaseous contaminants from an air stream.
[0009] Thus, the background art considered it necessary to treat or
coat urethane or polymer filter material, such as foam, with
activated carbon or other hydrocarbon adsorbent material in order
to have a satisfactory butane working capacity and satisfactory
hydrocarbon adsorption. Coated foams, however, can have higher
weight, can be less resilient and can be more apt to generate
particle contamination from flaking. Thus, it would be desirable to
have a lower weight and more resilient filter material with
satisfactory butane working capacity for use in evaporative
hydrocarbon emissions systems.
SUMMARY OF THE INVENTION
[0010] A first aspect of the invention is a method for removing or
extracting hydrocarbons from a gaseous stream emitted from a fuel
tank during refueling a motor vehicle, device or appliance with a
hydrocarbon-based fuel consuming engine. According to the method, a
filter is installed in a flow path established between the fuel
tank and an exhaust from the fuel tank. The filter comprises a
polymer network and has a butane working capacity on a weight
percent basis (W/W %) of at least 4.0 percent, more preferably at
least 8.0 percent.
[0011] The polymer network may comprise a foam, such as a polyether
or polyester polyurethane foam, with a pore size between about 3
and 300 ppi, preferably between about 20 and about 90 ppi. The foam
may be thermally or chemically reticulated. Alternate polymer
materials to form the polymer network include urethanes, melamine,
acrylics, polyethylenes, polyimides, polyvinyl acetate, polyvinyl
alcohol, ethylene vinyl acetate and combinations of polymers.
[0012] The polymer network alternatively may comprise a nonwoven
polymer, a collection of polymer particles, a collection of
shredded particles of foam, a monolith of foam, multiple layers of
foam, a coiled sheet of foam, or any combination thereof, that can
be loaded into an inner chamber of a housing or container so as to
have a sufficient air permeability.
[0013] Whether a foam, nonwoven or other polymer network is used,
preferably, the polymer network has an air permeability of 0.1 to
20 inches water pressure drop, most preferably 0.1 to 5 inches
water pressure drop.
[0014] A coating optionally may be applied to a portion of the
polymer network to adjust efficacy of the filter. The coating
optionally may include activated carbons, silicas, silicates,
aluminosilicates, filter agents, molecular sieves, flame
retardants, electrically conductive materials, antimicrobial
additives, germicides, pigments and colorants.
[0015] In a second aspect, the invention comprises a system for
extracting evaporative hydrocarbon emissions from a motorized
vehicle, device or appliance. In this system, a filter canister or
other container has a housing defining an inner chamber, an inlet
through which a gas stream containing a hydrocarbon enters the
inner chamber, and an outlet from which a gas stream exits the
inner chamber. A filter, such as described above, comprising a
polymer network and having a butane working capacity on a weight
percent basis (W/W %) of at least 4.0 percent, preferably at least
8.0 percent, is inserted into the housing.
[0016] The filter may be formed as a single unit or as a
combination of two or more filter units inserted into the housing.
For example, the housing inner chamber may be generally cylindrical
and the filter may be formed as one or more circular disks stacked
one atop the other and inserted into said inner chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention will be described in the following
detailed description with reference to the following drawings:
[0018] FIG. 1 is a schematic diagram of a fuel system with enhanced
evaporative emissions control for capturing hydrocarbon vapors
emitted during refueling which includes a filter canister
containing a filter material according to the invention;
[0019] FIG. 2 is a front elevational view in partial cross section
of a first embodiment of a filter canister containing a stack of
filter material disks according to the invention;
[0020] FIG. 3 is a cross-sectional view taken along line 3-3 in
FIG. 2;
[0021] FIG. 4 is a front elevational view of a second embodiment of
a filter canister containing a filter material according to the
invention;
[0022] FIG. 5 is a cross-sectional view taken along line 5-5 in
FIG. 4;
[0023] FIG. 6 is a schematic diagram of a dip and nip coating
apparatus;
[0024] FIG. 7 is a graph of Butane Working Capacity ("BWC") versus
Time in seconds comparing the butane absorption of urethane foam
and urethane foam coated with an activated carbon coating;
[0025] FIG. 8 is a graph of BWC in percent versus foam pore size in
pores per inch for coated and uncoated foams of varying pore
size;
[0026] FIG. 9 is a graph of maximum butane absorbed versus foam
pore size for coated and uncoated foams of varying pore size;
and
[0027] FIG. 10 is a graph of force versus strain showing hysteresis
curves for a polyurethane foam filter media as compared to a
conventional honeycomb carbon extrusion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Referring first to FIG. 1, a fuel system 10 with enhanced
evaporative emissions controls has a fuel tank 12 into which fuel
20 may be poured from pump nozzle 22 via fuel inlet 18. The tank is
provided with a fuel tank vent valve 24 in fluid communication with
a control valve 25 that in turn is in fluid communication with a
fuel tank vent tube and fittings 26 leading to the canister 14 that
is filled with an a filter 16. A canister vent valve 28 and purge
line 30 are provided as outlets from the canister 14. The canister
purge line 30 leads to a purge vapor management valve 32 in fluid
communication with a purge port 34 to the fuel injectors of the
engine 36 and the exhaust therefrom.
[0029] As liquid hydrocarbon fuel, such as gasoline, is pumped via
nozzle 22 into the fuel tank 12, the gas vapors in the vapor space
above the fuel in the tank are displaced by the liquid fuel 20.
Such displaced gas vapors are not permitted to escape from the fuel
tank to the atmosphere. Rather, such gas vapors flow from the tank
through the fuel tank vent valve 24 and control valve 25 into the
fuel tank vent tube and fittings 26 leading to the canister inlet.
The gas vapors pass through the filter 16 within the canister 14
wherein a substantial portion of the hydrocarbon species in the gas
vapors are drawn out of the vapor and attach to the filter 16. The
gaseous fluid emitted from the filter 16 then flows through the
purge line 30 and through the purge vapor management valve 32 to
the purge port 34 into the fuel injector manifold in the engine
36.
[0030] Referring next to FIGS. 2 and 3, a system for evaporative
hydrocarbon emissions control has a canister 14 that is formed as a
generally cylindrical housing from materials resistant to
corrosion, including aluminum, stainless steel, plastics and
composite materials. The housing defines a cylindrical chamber for
holding a filter medium. While the canister 14 is illustrated as
having a generally cylindrical shape, other cross-sectional shapes
are possible. The canister dimensions are selected so that the
canister will fit within space within the exhaust system and so
that the sufficient vapor flow rates through the canister may be
maintained.
[0031] The filter medium shown in FIG. 2 comprises multiple
cylindrical blocks 17 of urethane foam inserted inside the chamber.
The cylindrical blocks 17 are stacked one atop the other to fill
the chamber. For example, each cylindrical block may have a
diameter of about three inches and a thickness of about one inch.
The blocks may be of the same or different urethane foam or other
hydrocarbon absorbing material. The blocks may be of different
shape besides cylindrical to fit within chambers having different
inner housing configurations. Alternatively, the filter medium may
be formed as a one-piece block or monolith of foam that fills the
chamber.
[0032] Referring next to FIGS. 4 and 5, in an alternate hydrocarbon
evaporative emissions control system, the filter medium comprises a
sheet 16 of urethane foam that has been coiled or rolled like a
jelly roll to form a cylinder that fits within the cylindrical
chamber of the canister 14. For example, the sheet has a length of
8 to 16 inches, a width of 5 to 10 inches and a thickness of 0.25
to 1 inches, most preferably a length of 12 inches, a width of 6 to
7 inches and a thickness of 0.5 inches.
[0033] The filter medium may be formed of a urethane foam, wherein
"urethane" means generally the reaction product of an isocyanate
and a polyol that contains one or more hydroxyl groups. A preferred
urethane foam is a polyether polyurethane foam with a pore size in
the range of 3 to 200 pores per linear inch, more preferably from
20 to 90 pores per linear inch, and most preferably from 30 to 80
pores per linear inch. The preferred polyurethane foam has a
density in the range of 0.6 to 20 pounds per cubic foot, preferably
about 1.3 to 4 pounds per cubic foot.
[0034] An alternate urethane foam is a polyester polyurethane foam
with a pore size in the range of 3 to 200 pores per linear inch,
more preferably from 20 to 90 pores per linear inch, and with a
density in the range of 0.6 to 20 pounds per cubic foot,
preferably, 1.3 to 4 pounds per cubic foot.
[0035] The urethane foam optionally may be thermally or chemically
reticulated or networked to remove the cell windows, leaving a
network of strands or struts. Reticulation increases void volume
and air permeability. A thermal reticulation process is described,
for example, in U.S. Pat. Nos. 3,175,025 to Green, et al. and
3,171,820 to Volz, et al. A chemical reticulation process is
described, for example, in GB 858,127 to Scott Paper Company. Where
an ester polyurethane foam is selected for the filter medium, we
have found that hydrocarbon absorption is enhanced when such foam
has been chemically reticulated.
[0036] The filter medium also may be formed from other polymers,
such as other urethanes, polyethylenes, polyimides, melamines and
acrylics, polyvinyl acetates, polyvinyl alcohols, ethylene vinyl
acetates or combinations. The polymers may be foamed, or may be
formed into a nonwoven having sufficient fluid/air permeability to
serve as a filter. Needled or bonded nonwoven structures formed
from fibers or strands of the polymers may be used. U.S. Pat. Nos.
2,958,593, 3,324,609 and 4,490,425 describe various methods of
forming nonwoven fiber structures and fabrics.
[0037] In addition to a sheet of polyurethane foam or a polymeric
nonwoven, the polymer network forming the filter medium
alternatively may comprise a collection of polymer particles, a
collection of shredded particles of foam, a monolith of foam,
multiple layers of foam, a coiled sheet of foam, or any combination
thereof
[0038] While we have found that a urethane foam without any coating
achieves a desired hydrocarbon absorption and an effective butane
working capacity for use as a filter medium in an evaporative
hydrocarbon emissions system, it may be desirable to coat the foam
before use to vary its performance. If the foam is to be coated or
impregnated, one known method is a dip and nip method such as shown
in FIG. 6. In the dip and nip method, the foam sheet 40 is immersed
in a liquid mixture or slurry 42 of binder and optionally an
adsorbent, such as activated carbon, that is held in a tray 44. The
wetted foam sheet 40 is then compressed in the nip between a pair
of compression rollers 46. Excess slurry is squeezed out of the
wetted foam sheet and falls into a recycling tray 48. The dip and
nip may be repeated for multiple cycles to achieve a desired
coating loading. The impregnated foam is dried before it is
inserted into the filter canister chamber.
[0039] Representative coating binders include: acrylic binders,
acrylonitrile binders, epoxy binders, urethane binders, natural or
synthetic rubbers, PVC emulsion binders, and/or a blend of various
binders. Preferably the binders are water based emulsions. The
binders with or without added adsorbents may be applied to the foam
structure to adjust the hydrocarbon adsorption/absorption
efficacy.
[0040] Representative activated charcoals include: plant, wood
and/or other renewable material-sourced charcoals, and coal. These
activated carbon powders preferably have particle sizes in the
range of 100 to 400 mesh (4 to 150 micron), most preferably 325
mesh (45 micron or less). Automotive emission control grade
activated carbons are available from various supplies, including
MeadWestvaco, Norit, Calgon, Carbochem and Jacobi. One preferred
activated carbon available from MeadWestvaco (Covington, Va.) is
NUCHAR.RTM. SA, which has a minimum Iodine number of 900, an
apparent density of 21 to 23 lbs/ft.sup.3 (337-369 kg/m.sup.3), a
surface area of 1400 to 1800 m.sup.2/g and a pore volume to 1000
.ANG. of 1.1 to 1.3 (cc/g).
[0041] In addition to activated carbons or charcoals, other
possible adsorbents include silicas, silicates, such as
diatomaceous earth metals, filter agents, such as Celatom FW80
(CAS# 68855-54-9), and aluminosilicates, such as Fuller's Earth
(CAS# 8031-18-3) or Montmorillonite KSF (CAS#1318-93-0).
[0042] If a coating is applied to a foam, preferably, one or more
binders and one or more activated carbon powders or other
adsorbents are combined together with water to form a coating
mixture that may be impregnated into or coated onto the foam. In a
particularly preferred embodiment a rheology modifier or thickening
agent is incorporated into the coating mixture. Other additives may
be incorporated into the coating mixture, such as defoamers,
surfactants, wetting agents and dispersants.
[0043] The filter medium preferably has an air permeability from
0.1 to 20 inches water pressure drop, more preferably from 0.1 to 5
inches water pressure drop, most preferably up to 2 inches water
pressure drop. Typically, when a motor vehicle fuel tank is
refilled, the displaced vapors from the tank enter the filter at a
flow rate of about 200 cc/min. The hydrocarbon molecules in the
vapors attach to the foam filter. Thereafter, when the motor
vehicle engine is on, the engine pulls a vacuum and draws air at
20,000 cc/min through the filter. This larger flow rate pulls the
hydrocarbon vapor out of the filter and the hydrocarbon molecules
away from the filter medium (and the activated carbon if the filter
medium is coated), sending them to the engine for combustion. The
hydrocarbon absorbing sites are then available to absorb and/or
adsorb hydrocarbon molecules during the next refueling.
[0044] The filter medium has utility within evaporative hydrocarbon
emissions control systems used in various motorized vehicles,
devices and appliances, such as automobiles, sport utility
vehicles, boats, motor cycles, motor scooters, snow mobiles, snow
blowers, pick up trucks, all terrain vehicles, lawn mowers, chain
saws, power washers, and air blowers. The filter medium may be
installed within a canister or housing through which an air or gas
stream with entrained hydrocarbons may be passed to form a
hydrocarbon emissions control system.
[0045] The following examples further illustrate the present
invention. All parts and percentages are expressed by weight unless
otherwise specified.
EXAMPLES
Polyurethane Foam Compositions
[0046] Polyether polyurethane foam samples were prepared from the
following ingredients:
1 Parts per hundred Parts per hundred Component Ether Foam Graft
Ether Foam VORANOL 3010 polyol 100.0 85.0 HS-100 0.0 15.0 TDI 63.8
56.8 KOSMOS 5-N 0.31 0.31 THANCAT NEM 1.26 1.26 K-29 0.08 0.08
BLACK PIGMENT 4.88 4.88 L-620 0.94 0.94 C-124 0.79 0.79 Deionized
water 4.72 4.3
[0047] "Parts per hundred" denotes parts by weight per hundred
parts polyol. VORANOL 3010 is a polyether polyol from Dow Chemical
Company. HS-100 is a graft polyol from Bayer. Generally, a graft
polyol such as HS-100 increases the stiffness of the resulting
foam. TD80 is toluene diisocyanate also from Dow. KOSMOS 5-N and
K-29 are tin catalysts from Degussa. THANCAT NEM is an amine
catalyst from Air Products and Chemicals of Allentown, Pa. C-124 is
an amine catalyst from Crompton. L-620 is a surfactant from GE
Silicones (formerly Osi Specialties).
[0048] Polyester polyurethane foam samples were prepared from the
following ingredients:
2 Parts per hundred Component Ester Foam 1102-50A polyol 100.0 TD80
46.5 SE-232 1.0 33LV 0.3 THANCAT NEM 1.2 Deionized water 3.6
[0049] 1102-50A is a polyester polyol from Inolex. SE-232 is a
surfactant from GE Silicones. 33LV is a catalyst and THANCAT NEM is
an amine catalyst both from Air Products and Chemicals of
Allentown, Pa.
[0050] In the examples, the polyol(s), water, surfactants,
catalysts and pigments were mixed together in a first process
stream and combined with the isocyanate at the mixing head of a
conventional foam mixer. In some cases, foam densities were
adjusted by adjusting water level. The foaming mixture was
deposited from the mixer onto a moving conveyer and allowed to rise
at room temperature and pressure as it was conveyed away from the
mixer. The foam then was allowed to cure for 24 hours before
further processing.
[0051] To increase air permeability, some of the foam samples were
reticulated (either thermally or chemically as indicated below) to
remove cell windows from the foam structure to leave a network of
interconnected strands with voids therebetween. The voids create
fluid flow paths through the reticulated foam structure.
[0052] The Butane Working Capacity (BWC) on a weight percent basis
(W/W %) and butane absorption was evaluated for polyurethane foams
of varying pore size without any adsorbent coatings as reported in
Table 1 below.
[0053] A portion of the foam samples were also coated with an
activated carbon coating formulation as set out below.
Activated Carbon Coating Formulation
[0054]
3 Component Weight Percent NUCHAR .RTM. SA carbon 8.5 BYK-020 0.7
RHOPLEX E-358 16.0 RHOPLEX HA-12 9.0 ACRYSOL RM-825 Premix 30.5
Deionized water 35.3
[0055] The ACRYSOL.TM. RM-825 Premix consisted of 50% by weight
RM-825 with the balance (50% by weight) deionized water.
ACRYSOL.TM. RM-825 is a rheology modifier and thickening agent
available from Rohm and Haas Company of Philadelphia, Pa.
RHOPLEX.TM. E-358 and RHOPLEX.TM. HA-12 are acrylic binders also
available from Rohm and Haas Company.
[0056] NUCHAR.RTM. SA is an activated carbon available from
MeadWestvaco (Covington, VA.). Activated carbon powders are also
available from Carbochem (Ardmore, Pa.), and Norit (Atlanta, Ga.).
The NUCHAR.RTM. SA activated carbon powder had a Butane Activity of
61.3%, a surface area of 1926 m.sup.2/g, an Iodine number of 1213,
and a particle size such that 90% of all particles had diameters of
less than 50 microns.
[0057] BYK-020 is a defoamer available from BYK-Chemie
(Wallingford, Conn.).
[0058] The activated carbon, BYK-020, E-358 and HA-12 were mixed
with approximately one half of the water under ambient temperature
and pressure to form a slurry. The RM-825 Premix and remaining
water were then added to the slurry and the mixture was mixed with
a blender for approximately five to ten minutes to form the
activated carbon coating formulation.
[0059] The coating formulation was then poured into a holding
container or tray. Each sheet of reticulated polyether polyurethane
foam having dimensions of 12.times.18.times.0.5 inch was immersed
into the coating formulation and removed from the coating
formulation and passed through the nip between two compression
rollers to force the coating formulation through the thickness of
the foam sheet thereby coating the foam strands. For the examples,
a single impregnating step was used. Each coated foam sheet was
then oven dried at 170.degree. C. for twenty to thirty minutes.
[0060] Weight gain was calculated by weighing the foam sheet prior
to coating and again after coating (weight gain=(coated
weight-initial weight)/initial weight). The samples had coating
loadings (weight gains) of from 95 to 105%.
[0061] "Flake off" is a subjective standard graded as severe,
moderate, slight or none, and determined by collecting the
particles that fell from the coated foam as the foam was rolled to
form the cylinder shape. Coated foams that have excessive flake off
could lead to processing difficulties, such as but not limited to,
difficulty installing the coated filter into a canister. Severe
flake off also may lead to other difficulties, such as but not
limited to, reduced vibration stability, clogged vapor lines, and
faulty activation of engine warning lights. The solid:binder ratio
and/or percent pickup can be optimized to limit flake off.
[0062] Butane Working Capacity (BWC) on a weight percent basis (W/W
%) was determined according to the following procedure. This
procedure is a variant of ASTM D5228, which is the Standard Test
Method for Determination of the Butane Working Capacity of
Activated Carbon. Coated and uncoated foam samples were cut into
disk shapes having a diameter of about 3 inches and a thickness of
about 0.5 inch. The samples were dried in an oven at 120.degree. C.
for one hour, then cooled in a dessicator for 15 minutes. The tare
weight ("B") of an empty cylindrical canister (6 inches long with
an inner diameter of 3 inches) was recorded. Thirteen foam disks
were loaded into the canister one atop the other to fill the
canister volume. The filled canister was then weighed. The "initial
weight" ("C") of the foam-filled canister was recorded.
[0063] The foam-filled canister was then attached to a butane
source and purged with butane for 15 minutes. The setting on the
rotameter was 144 for a flow rate of 250 ml/min. The canister then
was closed with a stopper and removed from the butane source. The
butane-purged canister was then weighed and the "butane saturated
weight" ("D") was recorded.
[0064] The butane-purged canister was then attached to a nitrogen
gas source and purged with nitrogen for 30 minutes. The setting on
the rotameter was 150 for a flow rate of 400 ml/min. After the
nitrogen purge, the canister was closed with a stopper and removed
from the nitrogen source. The final weight of the purged canister
was recorded ("E").
[0065] The weight (grams) of butane absorbed was calculated as
"D"-"E". The weight (grams) of the foam filter medium was
calculated as "C"-"B". BWC on a weight percent basis (W/W %) was
calculated as grams butane divided by grams of foam filter medium,
which is then multiplied by 100%.
[0066] Each foam grade and pore size, coated and uncoated, was
tested using this procedure at least twice, and the average values
were recorded.
[0067] The honeycomb extrusion activated carbon filter medium
presently used in the automotive industry had a butane working
capacity of 7.0 to 8.0%.
[0068] The BWC values for filters with either uncoated or coated
foams according to the invention are set out in Tables 1 and 2 and
illustrated in FIGS. 7, 8 and 9.
4TABLE 1 Dynamic Butane Absorption Butane Dwell Uncoated BWC Coated
BWC Time (sec) g Butane (W/W %) g Butane (W/W %) 30 0.56 3.3 0.50
1.5 60 0.74 4.4 0.67 2.1 120 1.05 6.1 0.80 2.4 300 1.75 10.6 2.19
6.7 600 1.77 11.0 2.33 7.1 900 1.76 11.1 2.38 7.3
[0069] A polyether polyurethane foam of the formulation identified
above had a pore size of 45 ppi. The calculated surface area of the
foam was 848 ft.sup.2/ft.sup.3. The butane flow rate was 250
ml/min. The data from Table 1 are set out in graphical form in FIG.
7.
[0070] During fabrication and shipping, honeycomb extrusion
activated carbon filters are notably fragile and easily damaged. A
honeycomb extrusion was tested under compression according to a
test method set out in ASTM 3574 using a Zwick Z010 materials
testing machine. The 2.0".times.1.5".times.0.25" sample was
subjected to a low-velocity compressive force (2 inch per minute
cross head speed). As the compression force on the sample increased
over time, the strain and the force increased. At a strain of about
0.8%, the force started to drop, indicating that some layers within
the honeycomb had collapsed. On further compression, the force
required dropped further. At 7% strain, the honeycomb layers
completely collapsed, as the measured force was zero. In ASTM 3574,
hysteresis is the percent area between the IFD-strain curve and the
return curve. The hysteresis for the honeycomb was 100%. FIG. 10
shows the hysteresis curves for the honeycomb extrusion 60 and for
a comparison polyurethane foam filter media 62.
[0071] In comparison to the honeycomb extrusion, a polyurethane
foam filter media is resilient and readily fabricated and shipped.
A foam sample having dimensions of 2".times.2".times.1" was also
tested using the ASTM 3574 test method at a 2 inch per minute cross
head speed. At forces that compressed the foam sample to 80%
compression, the foam structure did not crumble (See FIG. 10). The
hysteresis for the polyurethane foam sample was 60%. A sample with
a lower hysteresis is more resilient and less subject to crumbling
upon fabrication and shipping.
5TABLE 2 BWC for Coated and Uncoated Foams with Varying Pore Size
Uncoated BWC Coated BWC g butane (W/W %) g butane (W/W %) Ether
foams Pore size reticulated (1.4 pcf) 20 ppi 1.74 9.8 1.9 5.9 30
ppi 1.81 10.6 2.0 6.0 45 ppi 1.81 10.6 2.3 6.9 60 ppi 1.98 9.9 2.6
6.9 80 ppi 1.82 9.1 2.6 6.5 88 ppi 1.82 11.4 -- -- Higher density
(4.3 pcf) 60 ppi 2.89 6.7 -- -- Nonreticulated (1.4 pcf) 20 ppi
1.79 10.8 -- -- 30 ppi 1.84 10.5 -- -- Lower density (0.7 pcf) 60
ppi 1.54 16.6 -- -- Graft Ether Reticulated (1.9 pcf) 25 ppi 2.02
9.0 -- -- Ester foams Reticulated (2 pcf) 20 ppi 1.30 6.1 -- -- 60
ppi 1.31 6.3 -- -- 75 ppi 1.48 5.8 -- -- (chem . . . ret.) 75 ppi
1.47 6.6 -- -- Nonreticulated (2 pcf) 75 ppi 1.48 5.9 -- --
Melamine foam Basotec 1.23 20.8 -- -- (0.6 pcf) Honeycomb Activated
carbon (Comparison) Small cylinder 2.15 7.5 -- -- 28.5 g Large
Cylinder 6.04 7.9 -- -- 76 g
[0072] The calculated surface areas for the different pore sizes
are as follows:
[0073] 20 ppi--325 ft.sup.2/ft.sup.3
[0074] 30 ppi--525 ft.sup.2/ft.sup.3
[0075] 45 ppi--848 ft.sup.2/ft.sup.3
[0076] 60 ppi--90 ft.sup.2/ft.sup.3
[0077] 75 ppi--1549 ft.sup.2/ft.sup.3
[0078] 80 ppi--1672 ft.sup.2/ft.sup.3
[0079] 90 ppi--1921 ft.sup.2/ft.sup.3
[0080] Polymer networks with a greater surface area that may be
contacted by the hydrocarbons entrained in a gaseous fluid stream
generally have higher hydrocarbon absorption. However, networks
with smaller pore sizes (e.g. 80 ppi and 90 ppi) can also have
lower air permeabilities, which can limit contact between the
hydrocarbons and the polymer material internal to the polymer
network, and thus reduce hydrocarbon absorption.
[0081] FIG. 7 is a graph of the dynamic BWC (W/W %) over time for
the coated and uncoated polyether polyurethane foam samples having
a pore size of 45 ppi.
[0082] FIG. 8 is a graph comparing the BWC (W/W %) for coated and
uncoated polyether polyurethane foams at varying pore sizes from 20
ppi to 80 ppi. In all cases, the uncoated polyurethane foams have a
higher BWC (W/W %).
[0083] FIG. 9 is a graph comparing butane absorption (in grams or g
butane) for coated and uncoated polyether polyurethane foams at
varying pore sizes from 20 to 80 ppi. The adsorbent coating
increases the adsorption of butane, but also increases sample
weight and results in other problems associated with coatings, such
as flake off. The uncoated foams have greater resilience, and do
not have particulates that may flake off during use.
[0084] Those seeking to develop a filter medium for evaporative
hydrocarbon emissions may tailor the performance by adding a
coating or an adsorbent coating. We have found that uncoated filter
media have excellent butane working capacity and satisfactory
hydrocarbon absorption to use in secondary evaporative emission
filters, among other uses.
[0085] The invention has been illustrated by detailed description
and examples of the preferred embodiment. Various changes in form
and detail will be within the skill of persons skilled in the art.
Therefore, the invention must be measured by the claims and not by
the description of the examples or the preferred embodiments.
* * * * *